M. Erbil

Adsorption and Corrosion Inhibition Effect of 1,1′-Thiocarbonyldiimidazole on Mild Steel in H2SO4 Solution and Synergistic Effect of Iodide Ion

Abstract The inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion behaviors of mild steel (MS) in 0.5 mol·L−1 H2SO4 solution was studied with the help of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) techniques. The effect of immersion time on the inhibition effect of TCDI was also investigated over 72 h. For the long-term tests, hydrogen evolution with immersion time (VH2–t) was measured in addition to the three techniques already mentioned. The thermodynamic parameters, such as adsorption equilibrium constant (Kads) and adsorption free energy (ΔGads) values, were calculated and discussed. To clarify inhibition mechanism, the synergistic effect of iodide ion was also investigated. The potential of zero charge (PZC) of the MS was studied by electrochemical impedance spectroscopy method, and a mechanism of adsorption process was proposed. It was demonstrated that inhibition efficiency increased with the increase in TCDI concentration and synergistically increased in the presence of KI. The inhibition efficiency was discussed in terms of adsorption of inhibitor molecules on the metal surface and protective film formation.

The effect of relative humidity on the atmospheric corrosion of defective organic coating materials: an EIS study with a new approach

The effect of relative humidity on the atmospheric corrosion of defective polyester-coated galvanized mild steel was investigated using electrochemical impedance spectroscopy. Measurements were carried out on samples which had been tested in an accelerated atmospheric corrosion test. The relative humidity was adjusted to the desired value (70, 80 and 100%) by means of water–glycerol mixture in 0.1 M ammonium sulphate solutions. The impedance diagrams (Nyquist plots) were simulated using Equivcrt program developed by Boukamp using a recognized model electrical analogue and semi-ellipse model developed by Erbil. It has been shown that the defective coating resistance and corrosion rate of metal under the coating changes with relative humidity. A new equivalent circuit model has been suggested and also a differential capacitance definition has been created in this equivalent circuit model and charge transfer resistance (Rct) is redefined in this study.

Investigation of suitable cathodes for the production of hydrogen gas by electrolysis

The anodic and cathodic behaviours of aluminium, iron, mercury steel (HgSt), chrome-nickel steel (CrNiSt) and platinum have been studied in a 2N NaCl electrolyte (pH = 5) by means of electrolysis. The potentials of the cathodes and the theoretical and experimental discharge potentials of the systems have been determined. The cathodic and anodic overpotentials produced on Al, Fe, HgSt, CrNiSt and Pt were predicted against a platinum anode and a platinum cathode, respectively. The amounts of hydrogen gas produced at different times on the cathodes at a constant potential were measured and the hydrogen yield was calculated. From the data obtained, it is suggested that Pt anode and Al or HgSt cathode, or Al anode and Pt cathode, couples should be employed for the best electrolysis system.

The Rhodanine inhibition effect on the corrosion of a mild steel in acid along the exposure time

The corrosion performance of a mild steel (MS) exposed to a 0.5 M HCl solution with various concentrations of Rhodanine (Rh) was studied by means of anodic and cathodic voltammetric curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. Rh makes the corrosion of MS in HCl solution decelerate with the exposure time so as to reach a protective value of more than 99% in 168 h. The adsorption of Rh molecules on the MS obeys Langmiur adsorption isotherm. Thermodynamic parameters, adsorption equilibrium constant (Kads), and standard free energy of adsorption (ΔGadso) were calculated and discussed. The high inhibition efficiency was discussed in terms of blockading the metal surface by the Rh molecules strongly adsorbing witch their active centers and thus forming a sufficiently effective protective film.

EIS study of the effect of high levels of NH3 on the deformation of polyester-coated galvanised steel at different relative humidities

Abstract The effect of SO2 on the degradation of polyester-coated galvanised steel at different relative humidities was investigated using electrochemical impedance spectroscopy. Measurements were performed on specimens which had been tested in an accelerated gaseous corrosion test. For this purpose the samples were subjected to SO2 gas for 16 days in atmospheric test cells with adjusted relative humidity (RH) from 60 to 100%. Subsequently, the impedance response of the coated material was measured and evaluated. The results indicated that the coating performance varies with RH. Thus, under condensing conditions, the organic coating and galvanised layer was totally removed, the impedance response being interpreted as the formation of an iron sulphide film on the surface. At lower RH, remarkably, the coating remained effectively intact with the coating resistance varying inversely with RH. This work is relevant to the application of such organic-coated products adjacent to combustion flues where high levels of SO2 occur in association with high humidity.

The effects of SO2 and NH3 on the atmospheric corrosion of galvanized iron sheet

Abstract The corrosive effects of SO2 and NH3 gases on zinc and galvanized iron sheet have been investigated. For this purpose, analytical and electrochemical methods were used in laboratory conditions with varying relative humidity values (70–100%). Electrochemically, the anodic current-potential curves of zinc have been obtained in solutions of different concentrations of sulphuric acid (0.50, 0.25, 0.10 M) and ammonia (pH = 13.20). The results indicate that, the corrosion rate of zinc and galvanized iron increases as the relative humidity increases in SO2 containing medium but the corrosion rate is not related much to relative humidity in NH3 containing environment. At the same time, it has been observed that zinc does not get passive in H2SO4 containing medium but it does become passive in ammonia solution. This passivation of zinc in NH3 is due to the formation of a complex [Zn(NH3)4(OH)2] on the metal surface by OH− and NH3.

The effects of sulphate ion on concrete and reinforced concrete

The effects of the sulfate ions and the pH on the strength of concrete and reinforcement steel have been investigated. Concrete and reinforced concrete samples prepared by using mixing water having different sulfate ion concentrations (standard, 400 ppm and 3,500 ppm) were cured in a water bath containing the same ion concentrations of mixing water or distilled water at two different pH values (8 and 5). The samples were exposed to the environments for 90 days. The compressive strength of concrete, pH values of bath, galvanic current changes and potentials (vs. Ag/AgCl) of reinforcing steel were measured. It was observed that the compressive strength of the concrete decreases as the SO{sub 4}{sup {minus}2} ion concentration increases. The galvanic currents were high for the first 28 days and then these currents decreased steadily. It was found that the potentials have been rising up to the passive potential of the reinforcing steel where the SO{sub 4}{sup {minus}2} concentration is low.

The primary study on the effects of primer alcohols on the hydrogen evolution reaction on silver electrode

Abstract The cathodic behaviour of silver in 0.01 M NaCl and 0.01 M NaCl +1.0 alcohols which are methyl, ethyl and propyl alcohols is investigated at pH 3 and 5 by means of electrolysis. The experimental (Eexp) and theoretical (Erev) discharge potential are determined in all solutions between Pt and Ag electrodes. The cathodic and anodic overpotentials on silver cathode were determined using a platinum anode. The hydrogen gas is produced on constant potentials (5.00 or 10.00 V ) on silver cathode. It is observed that the presence of alcohols decreases the anodic overpotential and increases the hydrogen yield in NaCl solution.

Anodizing and corrosion behaviour of aluminium

In this study, aluminum was anodized in 0.4 M H2SO4 + 0.145 M H3BO3 solution by means of potentiostatic method. In first step, the most appropriate conditions (anodizing voltage and period) were determined. The voltage-current behavior was investigated between 0 to 30 V and oxide formation potential (15 V) was determined. Then chorono-amperometric measurement was obtained at this potential during 2 hours. Therefore, anodizing process was applied at 15 V between aluminium anode and mild steel cathode. In the second step, the corrosion performance of non-anodized (Al) and anodized samples (Al2O3) have been investigated in 3.5% NaCl solution by using electrochemical impedance spectroscopy and polarization techniques. The interface between metal and solution was modeled with the equivalent circuit successfully. The circuit’s elements were calculated with Ivium Soft fitting program. The polarization curves were obtained between −1.8 V and 0.5 V potential ranges. The experimental results proved that the thickness and quality of oxide film was improved with help of anodizing process. Thus the corrosion resistance of anodized aluminum is significantly increased.

Effect of some primary alcohols on hydrogen yield on platinum cathode in chloride solution

Abstract The effect of some primary alcohols on hydrogen evolution has been studied in 0.01 M NaCl +1 M x alcohol (x: 0, methyl, ethyl and propyl alcohol) at different pHs (3, 5 and 8) and temperatures (25°C,50°C and 75°C) on Pt electrode at a constant potential (5.00 V ) using electrolysis. The theoretical (Erev) and experimental discharge (Eexp) potentials for these systems have been determined and the volume of hydrogen gas measured at periods of time. The yield of hydrogen gas was calculated for different temperatures. For this system, alcohol adsorbs on to the platinum surface in alcohol solutions and decreases the overpotential for anodic and cathodic reactions; so that the highest hydrogen yield is obtained in all alcohol solutions.